Synthetic fibers began to be produced industrially in 1938. At the moment, there are already several dozen species. It is common for all of them that the starting material is low molecular weight compounds that are converted into polymers by chemical synthesis. By dissolving or melting the obtained polymers, a molding or spinning solution is prepared. They are molded from a solution or melt, and then they are subjected to finishing.
Varieties
Depending on the features that characterize the structure of macromolecules, it is customary to subdivide synthetic fibers into hetero-chain and carbo-chain. The former include those obtained from polymers in whose macromolecules, in addition to carbon, other elements are present - nitrogen, sulfur, oxygen and others. These include polyester, polyurethane, polyamide and polyurea. Carbochain synthetic fibers are characterized by the fact that their main chain is built of carbon atoms. This group includes polyvinyl chloride, polyacrylonitrile, polyolefin, polyvinyl alcohol and fluorine-containing.
The polymers that serve as the basis for the production of hetero-chain fibers are obtained by polycondensation, and the product is molded from melts. Carbose chains are obtained by chain polymerization, and the formation usually occurs from solutions, in rare cases from melts. You can consider any one synthetic polyamide fiber, which is called siblon.
Creation and application
Such a word as a siblon is completely unfamiliar to many, but earlier on the clothing labels one could see the abbreviation VVM, under which was hidden a viscose high-modulus fiber. Then the manufacturers thought that such a name would look prettier than the siblon, which could be associated with nylon and nylon. The production of synthetic fibers of this type is carried out from a Christmas tree, no matter how fabulous it looks.
Features
A siblon appeared in the early 70s of the last century. It is an advanced viscose. At the first stage, cellulose is obtained from wood; it is isolated in pure form. The largest amount is contained in cotton - about 98%, but from the fibers of cotton and without this, excellent yarns are obtained. Therefore, wood is most often used to produce pulp, in particular coniferous, where it contains 40-50%, and the rest are unnecessary components. They are required to get rid of in the process of manufacturing synthetic fibers.
Process of creation
Synthetically, fibers are produced in stages. At the first stage, the cooking process is carried out, during which all unnecessary substances from the wood chips are transported into the solution, and long polymer chains are broken up into separate fragments. Naturally, it does not cost only hot water, additives of various reagents are made: soda and others. Only cooking with the addition of sulfates allows one to obtain cellulose, which is suitable for the production of siblon, since less impurities remain in it.
When the pulp is already boiled, it is sent for bleaching, drying and pressing, and then moved to where it is needed - this is the production of paper, cellophane, cardboard and fibers, that is, the main production. What happens to her next?
Subsequent processing
If you want to get synthetic and natural fibers, then first you need to prepare a spinning solution. Cellulose is a solid that is not easy to dissolve. Therefore, it is usually converted into a water-soluble ester of dithiofar acid. The process of conversion into this substance is quite lengthy. First, the cellulose is treated with hot alkali, followed by extraction, and unnecessary elements pass into the solution. After extraction, the mass is crushed, and then placed in special chambers, where pre-ripening begins - cellulose molecules are shortened by almost half due to oxidative degradation. Next, the reaction of alkaline cellulose with carbon disulfide occurs, which allows you to get xanthate. This is an orange mass similar to dough, dithioformate, and the starting material. This solution for its viscosity is called "viscose."
Next, filtering takes place to remove the last impurities. Dissolved air is released by “boiling” the ether in vacuum. All these operations lead to the fact that xanthate becomes similar to young honey - yellow and viscous. The dope is completely ready for this.
Fiber production
The solution is squeezed through the die. Artificial synthetic fibers are not just spun in the traditional way. This operation is difficult to compare with a simple textile, it would be more correct to say that this is a chemical process that allows millions of streams of liquid viscose to become solid fibers. In Russia, viscose and siblon are obtained from cellulose. The second type of fiber is one and a half times stronger than the first, is characterized by greater resistance to alkalis, the fabrics from it are hygroscopic, a lesser degree of shrinkage and creasing. And differences in the processes of viscose and siblon production appear at the moment when the newly-born synthetic fibers appear in the settling bath after the dies.
Chemistry to the rescue
To obtain viscose, sulfuric acid is poured into the bath. It is intended for the decomposition of ether, due to which pure cellulose fibers are obtained. If it is necessary to obtain a siblon, zinc sulfate is added to the bath , partially hindering the hydrolysis of the ether, so residual xanthogenate will be contained in the threads. And what does it give? Further, the fibers are stretched and molded. When there are xanthate residues in the polymer fibers, it turns out to stretch the polymer cellulose chains along the axis of the fiber, rather than arranging them randomly, which is typical for ordinary viscose. After drawing, the fiber bundle is cut into spatulas with a length of 2-10 millimeters. After a few more procedures, the fibers are pressed into bales. Tons of wood is enough to produce 500 kilograms of pulp, from which 400 kilograms of siblon fiber will be released. Cellulose spinning takes about two days.
What is next done with siblone?
In the eighties, these synthetic fibers were used as additives to cotton so that the threads would spin better and not break. Substrates for artificial leather were made from siblon, and they were also used in the manufacture of asbestos products. At that time, the technologists were not interested in creating something new; as much fiber as possible was needed to realize the idea.
And in the West in those days, high-modulus viscose fibers were used to produce fabrics that were cheap and durable compared to cotton, but at the same time absorbed moisture and breathed well. Now Russia does not have its own cotton regions, so the siblon has high hopes. Only the demand for it is not very great so far, since almost nobody is buying fabrics and clothes of domestic production now.
Polymer fibers
They are usually divided into natural, synthetic and artificial. Natural are those fibers, the formation of which is carried out in natural conditions. They are usually classified according to their origin, which determines their chemical composition, into animals and plants. The first consists of protein, namely carotene. It is silk and wool. The second consists of cellulose, lignin and hemicellulose.
Artificial synthetic fibers are obtained through the chemical processing of polymers that exist in nature. It is customary to include acetate, viscose, alginate and protein fibers. Sulfate or sulfite wood pulp are used as raw materials for their production. The production of artificial fibers is carried out in the form of textile and cord yarns, as well as in the form of staple fibers, which are processed together with other fibers in the process of production of various fabrics.
Synthetic polyamide fiber is obtained from polymers derived artificially. As the feedstock in this process, polymer fibers are used, formed from flexible macromolecules of a weakly branched or linear structure, having a significant mass of more than 15,000 atomic mass units, as well as a very narrow molecular weight distribution. Depending on the type, synthetic fibers are able to have a high degree of strength, significant in relation to elongation, elasticity, resistance to multiple loads, small residual deformations and quick recovery after unloading. That is why, in addition to being used in textiles, they found application as reinforcing elements during the manufacture of composites, and all this allowed the special properties of synthetic fibers to be made.
Conclusion
In the past few years, one can observe a very steady increase in the number of achievements in the development of new polymer fibers, in particular, para-aramid, polyethylene, heat-resistant, combined, whose structure is the core-shell, heterocyclic polymers, which include various particles, for example, silver or other metals. Now, nylon material is no longer the top of engineering, since now there are a huge number of new fibers.